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<B><A HREF="IFCONFIG.html">IFCONFIG(8)</A></B>		FreeBSD System Manager's Manual 	   <B><A HREF="IFCONFIG.html">IFCONFIG(8)</A></B>


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<H2>NAME</H2><PRE>
     <B>ifconfig</B> - configure network interface parameters


</PRE>
<H2>SYNOPSIS</H2><PRE>
     <B>ifconfig</B> <I>interface</I> <I>address</I><B>_</B><I>family</I> [<I>address</I> [<I>dest</I><B>_</B><I>address</I>]] [<I>parameters</I>]
     <B>ifconfig</B> <B>-a</B> [<B>-d</B>] [<B>-u</B>] [<I>address</I><B>_</B><I>family</I>]
     <B>ifconfig</B> <B>-l</B> [<B>-d</B>] [<B>-u</B>] [<I>address</I><B>_</B><I>family</I>]


</PRE>
<H2>DESCRIPTION</H2><PRE>
     <B>Ifconfig</B> is used to assign an address to a network interface and/or con-
     figure network interface parameters.  <B>Ifconfig</B> must be used at boot time
     to define the network address of each interface present on a machine; it
     may also be used at a later time to redefine an interface's address or
     other operating parameters.

     The following options are available:

     <I>address</I>
	     For the DARPA-Internet family, the address is either a host name
	     present in the host name data base, <B><A HREF="hosts.html">hosts(5)</A></B>,  or a DARPA Inter-
	     net address expressed in the Internet standard ``dot notation''.

     <I>address</I><B>_</B><I>family</I>
	     Specify the <I>address</I> <I>family</I> which affects interpretation of the
	     remaining parameters.  Since an interface can receive transmis-
	     sions in differing protocols with different naming schemes, spec-
	     ifying the address family is recommended.	The address or proto-
	     col families currently supported are ``inet'', ``atalk'', and
	     ``ipx''.

     <I>dest</I><B>_</B><I>address</I>
	     Specify the address of the correspondent on the other end of a
	     point to point link.

     <I>interface</I>
	     This parameter is a string of the form ``name unit'', for exam-
	     ple, ``en0''.

     The following parameters may be set with <B>ifconfig</B>:

     <B>alias</B>   Establish an additional network address for this interface.  This
	     is sometimes useful when changing network numbers, and one wishes
	     to accept packets addressed to the old interface.

     <B>arp</B>     Enable the use of the Address Resolution Protocol in mapping be-
	     tween network level addresses and link level addresses (default).
	     This is currently implemented for mapping between DARPA Internet
	     addresses and 10Mb/s Ethernet addresses.

     <B>-arp</B>    Disable the use of the Address Resolution Protocol.

     <B>broadcast</B>
	     (Inet only) Specify the address to use to represent broadcasts to
	     the network.  The default broadcast address is the address with a
	     host part of all 1's.

     <B>debug</B>   Enable driver dependent debugging code; usually, this turns on
	     extra console error logging.

     <B>-debug</B>  Disable driver dependent debugging code.

     <B>delete</B>  Remove the network address specified.  This would be used if you
	     incorrectly specified an alias, or it was no longer needed.  If
	     you have incorrectly set an NS address having the side effect of
	     specifying the host portion, removing all NS addresses will allow
	     you to respecify the host portion.

     <B>down</B>    Mark an interface ``down''.  When an interface is marked
	     ``down'', the system will not attempt to transmit messages
	     through that interface.  If possible, the interface will be reset
	     to disable reception as well.  This action does not automatically
	     disable routes using the interface.

     <B>media</B> <I>type</I>
	     If the driver supports the media selection system, set the media
	     type of the interface to <I>type</I>. Some interfaces support the mutu-
	     ally exclusive use of one of several different physical media
	     connectors.  For example, a 10Mb/s Ethernet interface might sup-
	     port the use of either AUI or twisted pair connectors.  Setting
	     the media type to ``10base5/AUI'' would change the currently ac-
	     tive connector to the AUI port.  Setting it to ``10baseT/UTP''
	     would activate twisted pair.  Refer to the interfaces' driver
	     specific documentation or man page for a complete list of the
	     available types.

     <B>mediaopt</B> <I>opts</I>
	     If the driver supports the media selection system, set the speci-
	     fied media options on the interface.  <I>Opts</I> is a comma delimited
	     list of options to apply to the interface.  Refer to the inter-
	     faces' driver specific man page for a complete list of available
	     options.

     <B>-mediaopt</B> <I>opts</I>
	     If the driver supports the media selection system, disable the
	     specified media options on the interface.

     <B>metric</B> <I>n</I>
	     Set the routing metric of the interface to <I>n</I>, default 0.  The
	     routing metric is used by the routing protocol (<B><A HREF="routed.html">routed(8)</A></B>).
	     Higher metrics have the effect of making a route less favorable;
	     metrics are counted as addition hops to the destination network
	     or host.

     <B>mtu</B> <I>n</I>   Set the maximum transmission unit of the interface to <I>n</I>, default
	     is interface specific.  The mtu is used to limit the size of
	     packets that are transmitted on an interface.  Not all interfaces
	     support setting the mtu, and some interfaces have range restric-
	     tions.

     <B>netmask</B> <I>mask</I>
	     (Inet only) Specify how much of the address to reserve for subdi-
	     viding networks into sub-networks.  The mask includes the network
	     part of the local address and the subnet part, which is taken
	     from the host field of the address.  The mask can be specified as
	     a single hexadecimal number with a leading 0x, with a dot-nota-
	     tion Internet address, or with a pseudo-network name listed in
	     the network table <B><A HREF="networks.html">networks(5)</A></B>.  The mask contains 1's for the bit
	     positions in the 32-bit address which are to be used for the net-
	     work and subnet parts, and 0's for the host part.	The mask
	     should contain at least the standard network portion, and the
	     subnet field should be contiguous with the network portion.

     <B>range</B>   Under appletalk, set the interface to respond to a <I>netrange.</I> of
	     the form startnet-endnet. Appletalk uses this scheme instead of
	     netmasks though FreeBSD implements it internally as a set of net-
	     masks.

     <B>phase</B>   The argument following this specifies the version (phase) of the
	     Appletalk network attached to the interface. Values of 1 or 2 are
	     permitted.

     <B>link[0-2]</B>
	     Enable special processing of the link level of the interface.
	     These three options are interface specific in actual effect, how-
	     ever, they are in general used to select special modes of opera-
	     tion. An example of this is to enable SLIP compression, or to se-
	     lect the connector type for some Ethernet cards.  Refer to the
	     man page for the specific driver for more information.

     <B>-link[0-2]</B>
	     Disable special processing at the link level with the specified
	     interface.

     <B>up</B>      Mark an interface ``up''. This may be used to enable an interface
	     after an ``ifconfig down''. It happens automatically when setting
	     the first address on an interface.  If the interface was reset
	     when previously marked down, the hardware will be re-initialized.

     <B>Ifconfig</B> displays the current configuration for a network interface when
     no optional parameters are supplied.  If a protocol family is specified,
     <B>ifconfig</B> will report only the details specific to that protocol family.

     If the driver does supports the media selection system, the supported me-
     dia list will be included in the output.

     Optionally, the <B>-a</B> flag may be used instead of an interface name.	This
     flag instructs <B>ifconfig</B> to display information about all interfaces in
     the system.  The <B>-d</B> flag limits this to interfaces that are down, and <B>-u</B>
     limits this to interfaces that are up.

     The <B>-l</B> flag may be used to list all available interfaces on the system,
     with no other additional information.  Use of this flag is mutually ex-
     clusive with all other flags and commands, except for <B>-d</B> (only list in-
     terfaces that are down) and <B>-u</B> (only list interfaces that are up).

     Only the super-user may modify the configuration of a network interface.


</PRE>
<H2>NOTES</H2><PRE>
     The media selection system is relatively new and only some drivers sup-
     port it (or have need for it).


</PRE>
<H2>DIAGNOSTICS</H2><PRE>
     Messages indicating the specified interface does not exist, the requested
     address is unknown, or the user is not privileged and tried to alter an
     interface's configuration.


</PRE>
<H2>SEE ALSO</H2><PRE>
     <B><A HREF="netstat.html">netstat(1)</A></B>,  <B><A HREF="netintro.html">netintro(4)</A></B>,	<B><A HREF="rc.html">rc(8)</A></B>,	<B><A HREF="routed.html">routed(8)</A></B>


</PRE>
<H2>HISTORY</H2><PRE>
     The <B>ifconfig</B> command appeared in 4.2BSD.

4.2 Berkeley Distribution      February 13, 1996			     3
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